And yet was it so surprising? In the US there are no secrets, only delayed disclosure. The intelligence and military oversight arrangements in Washington, the power of Congress, the openness of US society and the frenetic nature of the Washington news, policy and gossip mill, all mean few things stay secret for long.

I first experienced this decades ago when I sought use of some US surveillance assets for a hostage rescue mission in South America. "We can't do that," they said. "We have a large number of our own citizens held hostage there, and when it gets out that we helped you but didn't rescue our own, there'll be hell to pay." When I queried how top secret details would get out, they simply said: "This is Washington. Everything leaks."

We got our assets, and it did not leak. But they had a point. A large amount does leak, from the fine details of the killing of Osama bin Laden spun by the Obama administration, to myriad other operational data ferreted out by Washington's press corps. Sometimes it leads to tragedy, as when a mishandled freedom of information request led to the assassination of the CIA's Athens head of station in 1975. Mostly, however, it is as well-handled as it can be in such a determinedly open society.

Which brings us directly to a problem for the current British government. Today they present to the Commons plans to transform hearings of some civil lawsuits against the government into, effectively, secret courts. The primary justification is that the US intelligence agencies would cease to share information with the UK if our courts continue to be able to disclose data obtained from US sources.

This argument was blown out of the water by the disclosures about the British agent in Yemen, which demonstrate that the US system leaks far worse than the British ever could. This American leak happened not in the pursuit of justice, but as a casually irresponsible piece of political spin.It is an argument based on a series of falsehoods. Firstly, it assumes that the Americans had historically held a naive belief that the "control principle" was absolute. This is not so. Rather than listen to the spin of our government agencies read the evidence, given under oath by Morton Halperin, a foreign policy and security adviser to presidents Nixon and Clinton.

"The US government would not expect the UK government to provide greater protection to shared intelligence than provided by the US government itself," he said. "US law grants discretion to courts to determine whether specific intelligence is properly classified and withheld from the public, and to decide when criminal defendants must be shown classified information … It thus defies all reason to expect that the relationship between the US and the UK would somehow suffer if similar provisions in [UK] law … resulted in the public disclosure of shared information based on a judicial determination that the public interest demanded such disclosure."

So the claims of our government agencies are inherently implausible. Nevertheless, those agencies then claimed that the disclosures in the Binyam Mohamed case had already led to a drying-up of intelligence from the US agencies. Put to one side the fact that, as the suicide bomber case demonstrates, the US relies on our human intelligence as much as we do on their technical prowess – and so cutting cooperation would hurt them as much as us. Also put to one side that it was the US not UK courts that detailed how Mohamed had been tortured for two years. The British courts simply released a summary of these facts, and that after much deliberation. And leave aside the fact that the CIA's European director at the time has said that he "barely noticed" the revelations.

The nail in the coffin of this argument is that the CIA's press officer (yes, they have one) categorically denied that there had been any worsening of information exchange. So today the government, at the behest of the intelligence agencies, is going to ask us to introduce a secret procedure into our civil courts for the first time in our history. It will allow the covering-up of crimes such as complicity in torture that may have been carried out in our name. It is being justified as a way of protecting secrets from a country that makes a virtue of being even more open than we are, and which as a result lets slip more classified data in a day than our courts do in a decade.

Our courts do, however, expose wrongdoing, and civil litigation is an important method of exposing the wrongdoings of the state. A week after David Cameron apologised for the involvement of agents of the British state in the murder of Pat Finucane and the subsequent cover-up, he is asking MPs to agree to changes that will make exposure of such a cover-up less likely in future. A week after the government has paid out £2.2m to Sami al-Saadi rather than face in court the British government's complicity in his capture and torture by Gaddafi, David Cameron is asking us to allow future governments to ban exposure of such misbehaviour in open court.

It is hard to imagine what danger to national security would be posed by such a court case. It is easy to imagine it being politically embarrassing, however. But this is no excuse for doing serious harm to our justice system. What is being proposed is that evidence the government wants kept out of open court is not even shown to the people who have suffered wrongdoing, or to their lawyers. We know this system works badly because where it is operated, in terrorism control order cases, the lawyers the government employs to operate it say it doesn't work. The vast majority of these "special advocates" are adamantly against the government's proposals.

We should not kid ourselves that these legal changes are just dealing with issues in the past. The government's own independent adviser on security matters has told the joint committee on human rights that one reason for the government's pursuit of secret courts is to protect their position on the use of drones to assassinate alleged terrorists. The policy is controversial, not least because a number of those killed appear to be innocent bystanders. Are we going to deny them justice simply because of our craven relationship with the US?

It is being argued on the assumption that our allies are naive, and are willing to compromise the fundamental values of our justice system in a war that is supposed to be in defence of those very values. None of these arguments stand.

Cameron has quite properly received praise for his handling of the Finucane and Bloody Sunday inquiries. That will stand for nought, however, if in 20 years' time another inquiry lambasts his government for making it possible to cover up the misdeeds of modern times.

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